Finding Fuse Rating

abhinav.gupta88 · 18th May 2009, 23:49

Gurus

I wanted to know how exactly should be the fuse rating calculated.
i.e. What rating of fuse should be used in the fuse holder.

Is it according to the wiring used or according to the fuse rating on the amplifier(s)

Thanks in Advance.

panky12345 · 19th May 2009, 09:15

What I think is adding up the fuse ratings on all the amps that you're using and choosing a slighly lower rating fuse in the fuse holder (safety).

Say the total comes out to be 210 on all the amps.. then the fuse rating in the holder should be 200.

karankapoor · 19th May 2009, 09:25

no no panky its the other way, say if you are using 2 amps and there fuse rating are 200A then you should use atleast 225 A fuse or higher then this. reason if you use a lesser A fuse it will blow.

DerAlte · 19th May 2009, 10:14

It should be as per the fuse rating on the amplifier, and not the cable current rating. In most cases the cable can carry the full short circuit current for quite some time before insulation breakdown.

Ideally you should leave a 30% margin above the total current drawn. This is to take care of short-duration current overloads and heating up of the fuse under such conditions. If the consumption is 30% higher than normal for sustained periods, the fuse *should* blow. Current spike conditions (going up sharply and coming down sharply) should not blow the fuse, whereas short circuit conditions should blow it immediately.

Keep in mind the amp fuse (slow blow) and the fuse-block fuse you want to use (fast blow) are different types. The external fuse should blow only on short-circuit; the internal fuse of the amp is always designed to work for different conditions the amp faces.

panky12345 · 19th May 2009, 10:19

.. oops my bad! wanted to write the otherway. think I got up early today :-)

abhinav.gupta88 · 19th May 2009, 11:25

thanks guys. So for something with a total of 100 , one should use 30 percent more that is 130. Is that correct?

karankapoor · 19th May 2009, 13:05

As i earlier said if you amp fuse rating is 100 A you can use 125 or 150A inline fuse, but i doubt you can find inline fuse of that rating(130 A) they come as 100A/125A 150A/175A/200A. so go with 125 A fuse will work fine.

18th May 2009, 23:49	#1
abhinav.gupta88 Senior - BHPian Join Date: Sep 2007 Location: Delhi , India Posts: 4,092 Thanked: 325 Times View My Garage	Finding Fuse Rating Gurus I wanted to know how exactly should be the fuse rating calculated. i.e. What rating of fuse should be used in the fuse holder. Is it according to the wiring used or according to the fuse rating on the amplifier(s) Thanks in Advance.
	() Thanks

19th May 2009, 09:15	#2
panky12345 Senior - BHPian Join Date: Mar 2006 Location: New Delhi Posts: 2,697 Thanked: 171 Times	What I think is adding up the fuse ratings on all the amps that you're using and choosing a slighly lower rating fuse in the fuse holder (safety). Say the total comes out to be 210 on all the amps.. then the fuse rating in the holder should be 200.
	() Thanks

19th May 2009, 09:25	#3
karankapoor Senior - BHPian Join Date: Apr 2008 Location: in the car!!! Posts: 1,675 Thanked: 6 Times	no no panky its the other way, say if you are using 2 amps and there fuse rating are 200A then you should use atleast 225 A fuse or higher then this. reason if you use a lesser A fuse it will blow.
	() Thanks

19th May 2009, 10:14	#4
DerAlte Senior - BHPian Join Date: Mar 2007 Location: Bangalore Posts: 8,069 Thanked: 2,919 Times	It should be as per the fuse rating on the amplifier, and not the cable current rating. In most cases the cable can carry the full short circuit current for quite some time before insulation breakdown. Ideally you should leave a 30% margin above the total current drawn. This is to take care of short-duration current overloads and heating up of the fuse under such conditions. If the consumption is 30% higher than normal for sustained periods, the fuse should blow. Current spike conditions (going up sharply and coming down sharply) should not blow the fuse, whereas short circuit conditions should blow it immediately. Keep in mind the amp fuse (slow blow) and the fuse-block fuse you want to use (fast blow) are different types. The external fuse should blow only on short-circuit; the internal fuse of the amp is always designed to work for different conditions the amp faces. Last edited by DerAlte : 19th May 2009 at 10:20.
	() Thanks

19th May 2009, 10:19	#5
panky12345 Senior - BHPian Join Date: Mar 2006 Location: New Delhi Posts: 2,697 Thanked: 171 Times	.. oops my bad! wanted to write the otherway. think I got up early today :-)
	() Thanks

19th May 2009, 11:25	#6
abhinav.gupta88 Senior - BHPian Join Date: Sep 2007 Location: Delhi , India Posts: 4,092 Thanked: 325 Times View My Garage	thanks guys. So for something with a total of 100 , one should use 30 percent more that is 130. Is that correct?
	() Thanks

19th May 2009, 13:05	#7
karankapoor Senior - BHPian Join Date: Apr 2008 Location: in the car!!! Posts: 1,675 Thanked: 6 Times	As i earlier said if you amp fuse rating is 100 A you can use 125 or 150A inline fuse, but i doubt you can find inline fuse of that rating(130 A) they come as 100A/125A 150A/175A/200A. so go with 125 A fuse will work fine.
	() Thanks